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The mkiv Supra Owners Club

confused over diff codes


Jay_vr6

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Right I've done the usual searches and googled.

I have a 94 jap n/a, now the trans code on the car states A01B , now i've seen peeps say if it has an A at the end its open diff and B means lsd. As far as I can see mine is a torsion diff ? now this is where I'm confused, If it's a torsion diff, is it open or lsd ? I'm sure torsion is lsd but i didn't think many early n/a's came with them if at all.

I was just confirming before I went a splashed on a trd lsd.

I fit is a torsion lsd then upgrading to a trd be much point as its not pushing big bhp.

I was only thinking of upgrading to an lsd as my mk3 has one and it feels a hell of alot more grounded when driving quick.

Many thanks in anticipation :)

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The torsen diff from what I can ascertain about it isn't exactly brilliant. Thats why people put the TRD one in. If the VIN plate says its got an LSD then it should have a torsen LSD in it. Like I say they get tired and I think that is possibly whats wrong with mine. Someone from Tech could explain the exact workings of a torsen diff or you could google it and do some reading. Whatever the outcome though it all boils down to the same thing, if you don't like the diff you have, no matter what it turns out to be then changing it is a good idea.

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Yes a torsen diff is what people call a LSD.

Yes, some NAs came with them from new.

 

Does your NA have ABS too? Not many did but you may have a higher than average spec one.

 

I can think of a lot of other things to spend £600 on before I'd remove a perfectly good torsen diff and replace it with a TRD one, although the TRD are very good, apparently - is it worth it on an NA? (no offence like)

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Ah yeah Jake but that depends on if said torsen diff is actually limited slipping or not wouldn't it? If its driving cack in comparison to a mk3 (which I've owned as well) then it may not actually be limiting the slip anymore so yes I would justify the replacement of it. Even in an NA an LSD will make the car alot more driveable, after all they stuck one on the mk3's and they all had a max output similar to the mk4 NA

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Thinking about this more... a fairly common issue with the Torsen is they get more backlash as they wear. Try jacking up the rear with the handbrake off, rotate one wheel and see if there is any delay or kick before either the prop or other wheel tries to rotate. The backlash can be changed by adjusting the ring gear shims so if this is a cause it's a more cost effective solution (provided it's not too worn).

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Yeah that sounds like a good idea. How do you do that???

 

Erm, dunno! Mark (Phoenix) explained it once, it's something to do with fitting larger shims which space the ring gears closer to another set of gears in the diff. I forget their name too. There is apparently a limit to what adjustment that can be made as too close a spacing causes excessive heat and potential failure.

 

That’s possibly completely wrong or misinterpreted!

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aha this is more like it, the sup has some aftermarket wheels, +51 offset(at rear) with 265/35/18s i believe, they probably don't help. I was just assuming up till i knew I had the torsion diff that it was the open diff giving me some dodgy traction. hence checking before spending a whole lotta cash :)

 

it's just my mk3 which is/was knocking a healthy 300bhp was alot more settled and inspiring than my n/a mk4. suspension is stock and all in good working order.

Think I'll bowl down to the local man who does gearboxes and such for sports racing and let him check it out to see if its really worn.

Homer thanks for the tip I'll jack the car up and check the backlash and also my diff fluid level too :)

As for an lsd on a N/a, no offence but why not if it gives better traction over an open diff.

thanks for the feedback guys :) still new to this mk4 lark

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I know the chap had it all aligned before i brought it, all the tyres are showing even wear but maybe I'll have to have it rechecked, would changing the rear tyres to something less wide help at all ?

Also how can I check for abs, I'm sure i don't have it but I gather I can just check for the sensors on each hub ? I'm not going to boot it and stamp on the brakes to check :)

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Hi Jay,

 

Hope car isn't giving you any other troubles apart from not feeling as snug on the rear as your MK3, shame to hear that even :-(

 

You're right about tires, shocks etc, it was all properly aligned. I think I had the diff fluid changed about a year ago. Didn't bump into a single kerb or pothole since last alignment, but you know how it is with tracking. Yes the wheels are a lot bigger than OEM, I didn't change any of the geometry when getting these fitted, but the car came from japan with 18's (9.5J rear, now 10J rear), so it could have had some changes made for all I know. I just knew it wore nice and evenly, I felt the handling was fine, so if it ain't broke, don't fix it philosophy was taken :)

 

The car does *not* have ABS (after having someone pull out in front of my once at a very short distance) I found the fronts locked up (waits for someone to talk about cadence braking...)

 

I was on 245/40/18's when I started with the car, eventually going between 265-275/35/18's, and just found them more firmly balanced than the 245s.

 

I found the back end skitty and that's what caused me to change the shocks and upper wishbone arms, which I found cured the problems I had with rear-end instability.

 

Afraid I cannot 100% verify that it's not got an LSD on it, been in cars with LSD, have one now, and when I had the occasional slide due to cold weather/diesel/oil, the rear did handle like it didn't have an LSD, but this is just IMHO, I could be wrong. Always had it MOT'd assuming it was non-LSD, as didn't want them to test the rear brakes and do any damage..

 

Glad to see you on the forum bud

 

Si

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No worries Si, the cars great and it does def have an lsd, I'll swap out the fluid though at the weekend and fill it with lsd fluid. As for alignment its seems fine, my mk3 has 245/40/18's on the rear so i may try them if the offset isn't to big, otherwise I'll get the tyres moved over and see :) plus my mk3 is a damn sight heavier so I expect that helps too.

This is the fun when you haven't driven a completely stock car :)

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